In the application of lasers to uranium enrichment, as for example described in U.S. Pat. No. 3,772,519 or U.S. Pat. No. 3,939,354, commonly assigned to the same assignee as the present application, laser beams of very high intensity are ultimately desired for production scale enrichment. Such intensities may run higher than several Kw/cm.sup.2. Laser beam reflectors will become a necessary component of an efficient production level enrichment plant for such purposes as providing multiple reflections of the laser beam through each chamber, as illustrated in the above-referenced application, or for directing and guiding the beam throughout the enrichment plant.
The length of travel that an individual laser beam will experience in such a production plant, which is many meters of length, necessitates that the optical quality of the laser beam be maintained high to prevent uncontrollable spreading of the beam that would result in a loss of useful radiation over the extreme lengths to be encountered. The slightest distortion resulting from heating of reflectors carrying such high power densities can rapidly degrade the optical quality of the reflected beam to the point where it becomes difficult or impossible to use it over great distances. It becomes thus important to minimize the amount of energy absorbed as heat within the reflector and to remove as efficiently as possible what heat is absorbed. Under some circumstances it is also necessary to control the points of heat removal.
Conventional front face reflective surfaces are inadequate to this task because front reflection by even a high quality material, involves an inherent absorption due to the material resistivity which cannot be completely eliminated in practice. Also, such a reflective surface must be supported by a substrate which of necessity would remove the reflective surface by some distance from any cooling which could be applied to it.
In addition to uncontrollable expansion, conventional, rigid front surface reflector supports may, in the required high power application, lead to the generation of physical stresses within the reflective element in response to even slight thermal loss from the high power beams. Such stresses will tend to develop further distortions in the reflected beams.